**Background:** Lifestyle factors—physical fitness, dietary habits, mental stress, sleep quality, and smoking—are strong predictors of cardiovascular disease occurrence, clinical course, and treatment outcomes. Despite their undisputed relevance, these factors are rarely monitored systematically in daily clinical practice. Non-adherence to long-term self-reporting is common, and existing studies have focused on short monitoring periods (1–12 weeks) and single lifestyle domains. The Care-On trial addresses this gap by evaluating adherence to a continuous, unobtrusive, multi-domain lifestyle monitoring system over one year in cardiac patients.
**Methods:** This monocenter prospective observational trial plans to recruit 100 patients scheduled for or recently undergoing major cardiac interventions (CABG, FFR/PCI, EP/RFCA, TAVI, valve surgery) at Maxima Medical Center (Eindhoven/Veldhoven, Netherlands). Inclusion criteria: age ≥18 years, able to speak/read Dutch, willing to provide informed consent. Exclusion criteria include no internet connection, no computer/tablet/mobile phone, inability to wear activity tracker, life expectancy <1 year, physical impairments interfering with monitoring, and mental incompetence. The monitoring system comprises: (1) a wrist-worn Philips Health Band collecting continuous objective data (activity counts, heart rate, respiration rate, energy expenditure, steps, sleep); (2) a chatbot ('Caro') collecting self-reported dietary habits (24-hour food diary based on Dutch Dietary Guideline 2015 and Eetscore FFQ), mental stress (PANAS-based EMA, 3×/day), and sleep (Consensus Sleep Diary, 5 items); (3) a personal dashboard visualizing adherence and lifestyle data; and (4) an optional goal tracking module. The monitoring scheme runs 7 days per month (split over 2 weeks: 4 days week 1, 3 days week 2) for one year post-intervention, with the health watch worn during chatbot-active weeks. Periodic lifestyle assessments (FitMáx, NutriMáx, PSS-10, PSQI, smoking status) occur at baseline, 1 week, 3, 6, 9, and 12 months. The primary outcome is adherence (dichotomous: continued use at 1-year follow-up). Adherence is classified as low (<50%), moderate (50–75%), or high (>75%) based on a composite score of chatbot compliance, health watch wear time, and quarterly assessment completion. Patients below 50% are contacted once; non-resumption after 1 month classifies as non-adherent. Secondary outcomes include system usability (SUS), predictors of adherence (demographics, QoL [SF-12], self-efficacy [GSES], depression/anxiety [HADS], motivation, fatigue [FAS], mobile device proficiency [MDPQ-16]), and association between baseline lifestyle and clinical outcomes (re-hospitalizations, QoL). Sample size: 100 patients, anticipating 50% dropout at 1 year, providing ±10% precision (95% CI [0.398, 0.601]). Analysis uses multiple logistic and linear regression in SPSS v24.
**Clinical Implications:** The Care-On trial is among the first to evaluate long-term adherence to multi-domain lifestyle monitoring after major cardiac events. If successful, the system could enable better self-management, personalized cardiac rehabilitation, early detection of clinical deterioration, and improved long-term outcomes. The user-centered design (low burden, tailored monitoring schedule) aims to overcome poor adherence seen in conventional cardiac rehabilitation programs. Insights into predictors of adherence may allow personalization of monitoring strategies, potentially reducing healthcare costs and improving patient-relevant outcomes.